1. Field of the Invention
The present invention relates generally to energy efficient buildings and more specifically to a wall baffle system, which decreases the amount of heat loss through a vertical wall of a building.
2. Discussion of the Prior Art
Porous types of insulation such as fiberglass and mineral wool insulation have a problem of degraded performance in wall cavities and partially vertical wall and roof cavities. Heat rises in gasses and in liquids due to heat energy exciting the molecules in the matter, which causes the matter to expand and become less dense in the molecules above the source of heat. This lower density causes the gasses and liquids with the higher heat energy to rise as the cooler, denser molecules fall downward due to the effects of gravity and the less dense, more buoyant molecules rising to the top of gases and liquids. Like a hot air balloon, adding more heat into it decreases the density of the gases inside the hot air balloon. Once the gravitational force holding the balloon down is offset by the forces of the encapsulated lower density gasses rising upward in the cooler, denser air outside the balloon, the balloon rises in the opposite direction of the gravitational forces.
This same effect takes place inside of wall and roof cavities in air permeable insulation materials such as fiber glass and mineral wool insulation. While these materials generally have the most economic thermal insulation costs, the angle at which they are installed affects the performance of such assemblies. If one tests the performance with heat flow in the same downward direction as gravitational forces, you will get the highest resistance value as the natural heat direction is upward, opposite that of the natural flow of heat rising due the gravitational forces at work. The thermal resistance performance would be the optimum it could be.
If one tests the performance with the heat flow opposite the force of gravity, upward and in the same direction as the natural flow of heat, more heat will flow through the porous material as there is less resistance, because the heat is rising parallel with the natural flow of the heat upward. This will perform slightly less than the first example because the heat flow is faster when it flows in the same direction, as it's natural direction, so it has less resistance to flow. The heat simply does not have to fight the natural flow of heat in the same direction; so more heat would pass through the porous material in such an assembly.
If one tests the heat flow through porous materials in a horizontal direction, such as through a vertical wall, the performance can degrade significantly more. The reason for this added loss of performance is that the heat exposed to one side of a test sample assembly representing a vertical wall attempts to move to the point of lower energy on the cold side of the test specimen. This is the natural tendency of energy attempting to reach a point of equilibrium with all lower points of energy around it. There is a gradient that forms which follows the path of the energy from higher to lower energy. The path of this energy gradient varies significantly in porous insulation materials because the heat flow is improperly assumed to be generally linear from the closest points between the hot and the cold surfaces. This is simply a wrong assumption. What actually happens is that when the heat energy passes horizontally through the warm side air barrier of a porous insulation materials assembly, the heat energy immediately turns upward opposite the forces of gravity, rises and adds to the heat volume, which passed through the test sample air barrier directly above the first and lowest area unit of a heat entrance, and so on. This additive effect, like adding heat into a hot air balloon, is the same natural tendency of the heat energy to rise in gasses and liquids due to density changes caused by the added energy. The cumulative forces of the additive units of heat entering from the warm surface increases with the uninterrupted height of the sample vertical wall assembly. So the heat rises inside of the air porous wall test assemblies and the cumulative additional heat energy increases as the force and speed of the heat flow inside the test wall sample rises upward through the porous insulation material, opposite the force of gravity. This differs from the horizontal sample that does not have the cumulative effect as each unit of surface area is generally independent of the each other, with the heat rising parallel and opposite with the gravitational forces downward.
The net effect of the heat flow through the vertical assembly with air porous insulation is that the force and speed of the heat flow increases over the vertical distance of uninterrupted flow. So the heat flow rate at the bottom of the test assembly would be the lowest and the heat flow rate at the top of the test sample would be the highest due to the natural flow of heat opposite the force of gravity in the air porous insulation. Although these heat directional forces may be small individually, it is the accumulation or additive effect that can reduce the overall thermal resistance performance of the assembly as is seen in hot box tests of these air porous insulation assemblies. Data collected inside the walls of actual buildings with porous insulation, fiberglass, confirm that there is up to 40 degrees temperature difference inside the wall from the bottom to the top of a 20 foot high metal building wall. Heat rises vertically inside the air porous insulation materials and assemblies. It must then be assumed that the rate of heat flow changes with the angle of the assembly from vertical, highest flow rate, to the horizontal, the lowest flow rate. This is due to the cumulative forces and the increased flow rate of the heat rising inside the vertical assembly containing the porous insulation material. The density of the porous insulation material will also have an effect on the rate of flow and the thermal performance resistance in a particular assembly.
Metal buildings generally have horizontal conductive, steel girts nominally every six feet apart vertically. To these girts are typically attached conductive metal panels of some type. Typically these conductive girts pass horizontally through the thickness of most of the insulation. The heat flow upward inside of these metal building walls encounters these highly conductive steel members which are typically colder than the inside building temperature in the heating season. Correspondingly, the girts would be hotter than the interior building temperatures in the cooling season and the heat flow would be in the opposite direction, outside to inside. The effect of these highly conductive steel girts is to absorb some of the energy accumulated and rising with increasing force and speed inside of the vertical, porous insulation wall assemblies. The girts quickly absorb and conduct the heat to the colder side where it is radiated into the cooler environment. Hot box tests of metal building indicate a 20% to 30% reduction in performance as compared to the horizontal testing of identical and similar assemblies. It is expected that the rate of heat flow increases with the uninterrupted height of the vertical wall assembly with the porous insulation material.
This loss of thermal performance of wall assemblies with porous insulation results in reduced thermal performances of these assemblies and higher energy costs.
There is a difficulty in meeting minimum energy code criteria set for these type of assemblies with porous insulation inside them, because the insulation thickness required exceeds the space available to achieve the very low rates of heat flow or high insulation resistance. Installations at angles to the vertical would also have a progressively decreasing effect from these additive effects of the heat; because the heat becomes less additive, the more the assembly is positioned horizontally.
So there is a need for structures and methods which block the additive effect of the energy rising in the vertical wall assemblies of buildings and also of angled assemblies of buildings to reduce the accelerated heat loss caused by the increase of the forces and of a rate of speed of the heat movement through these assemblies containing porous insulation materials. There is also a need to block the heat from contacting the conductive girts in the building walls, which readily absorb and conduct the heat energy to the colder environment. There is also a need to divert the path of the heat flow direction back toward the warm side using sloped diverters or baffles, which will result in less heat loss to the colder environment absent the diversions which create resistance. There is also a need to increase the effectiveness of the diversion means by making the surfaces energy reflective such as polished aluminum foil.
Installations at angles to the vertical would also have a progressively decreasing effect from these additive effects of the heat because the heat becomes less additive the more horizontal the assembly is positioned.
Accordingly, there is a clearly felt need in the art for a wall baffle system, which includes inserting a plurality of reflecting insulation panels between horizontal girts adjacent an outer wall and attaching thermal blocks to a bottom of horizontal girts to block the absorption of upward heat flow adjacent the outer wall to decrease the amount of heat loss through the outer wall of a building and to meet energy code criteria within the existing thickness space inside these building walls.